[Python-Dev] Decimal data type issues (original) (raw)

Andrew P. Lentvorski, Jr. bsder at allcaps.org
Thu Apr 15 02:05:27 EDT 2004

On Tue, 13 Apr 2004, Batista, Facundo wrote:

The issue is that this limit is artificial: As long it's a long, you should be able to make it as big as your memory let you.

I agree with Tim that underflow/overflow are useful flags of something going wrong. Very few people would connect Decimal overflow with "Gee, why is Python allocating all of my system's memory?" I would like to see a soft default limit that can be modified.

As for the value of the default limits, I would actually choose both a default precision and exponent limit which would be within the range represented by a double precision floating point number.

This helps in two cases:

  1. People will try to interconvert FP and Decimal at various points. Having one with a significantly different range will certainly give some surprises. (example: Decimal would get converted to double precision FP before being used in OpenGL or Direct3D to draw a pie chart, graph, etc.)

  2. Having a default range somewhere inside double precision means that some mythical "efficient" implementation could actually use double precision FP operations to get close and then use a cleanup step to check the final digit. (Very useful for exponentials)

-a

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